This invention is directed to belting for use as timing belts, which incorporate a cloth or fabric layer on the teeth of the belt, and to improved fabric adhesion, when the belt is an ethylene-alpha-olefin elastomeric composition, such as EPDM (ethylene propylene diene terpolymer, by the use of, preferably, a combination of the use of a resorcinol formaldehyde latex (RFL) treatment for the fabric and the use of zinc diacrylate (ZDA).
Ethylene-alpha-olefin elastomeric compositions, which are readily processed, should have adequate mechanical properties in dynamic applications and acceptable adhesion to textile reinforcement materials to enable its use as the primary base elastomeric composition in applications such as belting including power transmission and flat belting, air springs, engine mounts. But, they have not found much success.
The use of salts of alpha, beta-unsaturated organic acids in elastomeric compositions is known. For example, Yarnell et al, U.S. Pat. No. 5,610,217, teaches an elastomeric material for use as the primary elastomeric composition in articles subject to dynamic loading, which comprises an ethylene-alpha-olefin elastomer composition capable of maintaining excellent abrasion resistance, pilling resistance, tensile strength, cut-growth resistance, modulus and adhesion to reinforcement materials under high and low temperature dynamic loading conditions. The elastomeric material is cured using a free radical promoting material, and comprises the reaction product of 100 parts by weight of an a ethylene-alpha-olefin elastomer which serves as the primary elastomer of the composition, from about 1 to about 30 parts per hundred weight of the elastomer (phr) of a metal salt of an {acute over (α)}-β-unsaturated organic acid, which includes zinc diacrylate, although zinc dimethacrylate is most preferred, and from about 25 to about 250 phr of a reinforcing filler.
The use of resorcinol-formaldehyde latex is known also for use in treating fabrics. For example, Knutson, U.S. Pat. No. 6,695,733, teaches treating carbon fiber tensile cord with RFL in making low growth power transmission belts. Fujumoto et al, U.S. Pat. No. 6,641,905, also teaches RFL treated polyester fiber cords for use in power transmission belts wherein the rubber latex is a chlororsulfonated polyethylene and alkylated chlorosulfonated polyethylene. Fujita et al, U.S. Pat. No. 5,609,243, teaches RFL treated fabric for toothed conveying belts. Takada et al, U.S. Pat. No. 6,294,600, teaches ethylene-{acute over (α)}-olefin elastomer and N,N′-m-phenylene dimaleimide compositions surfaced by RFL treated canvas cloth for use as power transmission belting. Hasaka et al, U.S. Pat. No. 6,524,417, teaches the use of RFL treated fiber material for use in ethylene-{acute over (α)}-olefin elastomer latex which is cured by vulcanization bonding and used in power transmission belts. Di Meco et al, U.S. Pat. No. 6,656,073, teaches a toothed belt where the toothed portion is covered with a cloth having a specific weft and warp design for the cloth, but where the cloth is treated with a RFL composition.